Electric discharge tube



1952 A. J. w. M. VAN OVERBEEK 2,517,078

ELECTRIC DISCHARGE TUBE Filed Dec. 20, 1949 Q9 iifg 33' INVENTOR.

ADRIANUS JOHANNES WILHELMUS MARIE VAN OVERBEEK Patented Nov. 4, 1952 beek, Eindhoven,

Netherlands, assignor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application December 20, 1949, Serial No. 133,994 In the Netherlands December 24, 1948 6 Claims.

The invention relates toelectric discharge tubes in which the electrons emanating from a cathode are concentrated into a beam adapted to be deflected by electrodes which are arranged on either side and to which alternating voltages are supplied.

Many embodiments of discharge tubes of the aforesaid kind are known for television, oscillography and amplification.

Applying alternating voltages to the deflecting electrodes permits of the beam being deflected at right angles to its direction of propagation. If the beam is required to be deflected in more than one direction, provision is made of more than one deflection system. Thus, for example, it is common practice to produce the deflection by four electrodes constituting two systems arranged in the tube at right angles to one another.

The deflection systems for deflecting the electrons in one direction have sometimes been formed by more than two electrodes in order to 'ensure particular properties of the discharge tube. Thus, for example, it has been suggested to subdivide one or both of the two deflecting" electrodes and to connect each of the electrodes thus formed to a wire taken to the outside of the tube. The beam may thus be deflected in the same direction under the action of several voltages fed to the various electrodes.

It is furthermore known to subdivide the electrodes to neutralize the so-called zero point anomaly. In a further alternative, the deflecting electrodes have been subdivided in order to ensure non-linear variation of the deflection with the voltage applied.

It is known from British Patent specification 485,298 to build up a deflection system for unidirectional deflection of the beam from more than two electrodes which are interconnected in a manner such that a number of successive deflection fields are produced which at any moment are of equal strength but of opposite sense. This subdivision is intended to ensure unidirectional deflection when the voltage fed to the deflecting electrodes has a period of the same order as the time in which the electrons pass through the deflection system.

Researches which have led to the invention to be described hereinafter have revealed that with high frequencies of the deflection voltages, losses occur which may be accounted for as follows:

For producing the electric field the condenser formed by the deflecting electrodes opposite one another must be charged. This charge must be supplied through the supply conductors for the deflecting electrodes. The resistance of these conductors gives rise to losses which at high frequencies may become very material since their increase is approximately proportional to the square of the frequency. They show themselves, for example, as damping of the circuits, connected to the deflecting electrodes.

The lower the charge to be supplied by way of the supply conductors, the smaller are these losses. This end may be achieved by reducing the deflecting electrodes in dimensions. However, this lowers the sensitivity of the deflection system.

The object of the invention is to ensure the same deflection sensitivity with lower charges.

In an electric discharge tube according to the invention for use at high frequencies an electron current concentrated into a beam is deflected with the use of deflecting electrodes to which the alternating voltages are supplied, and which are not located opposite one another on either side of the beam, but which are shifted relatively to one another in a direction parallel to the direction of the electron beam. The deflection system furthermore comprises at least one pair of directly inter-connected auxiliary deflecting electrodes, which are also shifted relatively to each other, each of the deflecting electrodes having arranged opposite it at least one auxiliary deflecting electrode.

The invention is based on the fact that each charge of a deflecting electrode induces an opposite charge in the opposite electrode. If, for example, at a given instant a positive charge is fed to a deflecting electrode, a negative charge is induced in the opposite auxiliary electrode. Since this auxiliary electrode is directly connected to the other electrode with which it forms a pair, the latter auxiliary electrode is given a positive charge. Arranged opposite this electrode is an electrode having a negative charge.

The auxiliary deflecting electrodes may be directly interconnected either internally or externally of the tube, it being, however, essential that they should be interconnected directly and that the connection should be practically free from losses. Both the deflecting and the auxiliary deflecting electrodes may be arranged internally or externally of the discharge tube.

In order that the invention may be readily carried into effect, a number of examples will now be described in detail with reference to the accomp anying drawings inwhich:

Fig. 1 showsdiagrammatically the construction of an electric discharge tube having an electron current concentrated into a beam and Figs. 2 to 9 show diagrammatically the arrangement of a number of deflection systems.

Referring to Fig. 1, the reference number I designates a cathode, 2 a Wehnelt cylinder and 3 an acceleration and concentration system built up from various electrodes; 4 and 5 designate deflecting electrodes to which a deflecting voltage is applied from a source 50; 6 and 1 designate a pair of suppressor electrodes to which the beam may be directed alternatively under the action of the voltages of the electrodes 4 and 5.

As an alternative, the anodes 6 and '1 may be replaced, for example by a luminescent screen.

Although Fig. 1 shows one deflection system. a plurality of systems may be provided between the electrodes 3 and the anodes 6 and I.

Fig. 2 shows a deflection system built up from two deflecting electrodes 8 and 9 and two auxiliary deflecting electrodes and H. These auxiliary deflection electrodes are directly interconnected electrically, electrodes 8 and 9 being connected to a source 50 of signal voltage. The operation of this deflection system may be described as follows:

If a positive charge is supplied to the electrode 8, it induces a negative char e of equal value in the electrode 10. A positive charge of enual value is thus set up at the electrode ll. Since the electrode H (which consequently has a positive charge) is arranged on the same side of the beam as the electrode 8 and is opposite the electrode 9, which has a negative charge when electrode 8 has a positive charge. it amplifies the deflection of the beam produced by this electrode. (In this case it is immaterial Whether the electrodes 8 and 9 are used in pushpull connection or whether one of the electrodes is earthed). The deflection of the total system is therefore canal to twice the deflection which would be obtained if electrode 8 were arranged directly opposite electrode 9. However, the charge reouired for building up the deflecting fields between electrodes 8 and ID, or 9 and II respectively is unaltered. Consequently, for twice the deflection the same charge has been suppliedso that the losses are halved for the same deflection. The required deflection voltage is hi her, but in most cases this is less inconvenient than a high current strength.

Fig. 3 illustrates how the principle underlying the construction shown in Fig. 2 may be applied to a deflection system extended to comprise more than four electrodes. The deflecting electrodes are designated I2 and I3 to which a signal volt-age is applied from a course 50. The deflection system comprises in addition four auxiliary electrodes, namely two pairs which are designated I4, I and I6, I 1 respectively. For the same deflection this system requires only one third of the charge which would be required to be supplied if electrodes [2 and I3 were arranged opposite one another.

Fig. 4 shows an alternative embodiment of a deflection system adapted for use in a tube according to the invention. In this system the auxiliary electrodes l8 and 19, 20 and 2|, 22 and 23 each form a pair. In this embodiment,

, the charge for building up the field is one fourth 50, were arranged opposite one another.

It is obvious from Figs. 2, 3 and e that both the deflecting electrodes and the auxiliary deflecting electrodes are shifted relatively to one another in a direction parallel to the direction of the electron beam.

The deflection system described with reference to Figs. 2, 3 and 4 may be used, if the periods of the supplied alternating deflecting voltages are high compared with the transit time of the electrons through the deflection system. This is also apparent from the potentials of the various electrodes. At a given instant, all the electrodes having a positive charge are on one side of the beam and the electrodes having a negative charge on the other side. As has been set out in British specification 485,298, it is necessary to subdivide the deflecting electrodes, if the periods of the alternating deflecting voltages become of the same order of magnitude as the transit time of the electrons. The principle of the said British patent specification may be combined with the principle underlying the present invention. Several deflection systems in which both principles are employed are shown in Figs. 5, 6, 7 and 8.

Fig. 5 shows a deflection system which comprises a total of three electrodes; 26 and 2'! designate the deflecting electrodes to whichv the alternating voltages are fed from a source 50. Electrode 28 is built up from two auxiliary deflecting electrodes arranged side by side. Since two auxiliary deflecting electrodes which form a pair are interconnected directly, two auxiliary deflecting electrodes arranged side by side may be replaced by one electrode. This results in an electrode system which is readily built up. In the system shown in Fig. 5, the electrode 28 has a length which is approximately determined by the formula jected to a deflection in a given direction will be subjected by system 27, 28 to deflection in the same direction since, in the time in which the electron has travelled from. a point in system 26, 28 to a corresponding point in system 21, 28 the deflecting voltage has been subjected to a phase shift of 180. The system shown in Fig. 5 is equivalent to the system shown in Fig. 2. A positive charge on the electrode 26 induces a negative charge in the left-hand half of the electrode 28; this results in a positive charge in the right-hand half of this electrode which is opposite electrode 21, which at this instant has a negative charge.

Fig. 6 shows a deflection system which is equivalent to the system shown in Fig. 3. As in the system shown in Fig. 5, the deflecting electrodes 29 and 3| to which an alternating voltage from a source 50 is applied have a length, in the direction of the electron beam, of approximately /2 A. The auxiliary deflecting electrodes 30 and 32 may again be assumed to be built up from two halves which are directly interconnected and which are shifted parallel to the di '5 rection of the electron beam. They have, consequently a length of A.

Fig. '7 shows an electrode system which, in effect, constitutes a doubling of the electrode system shown in Fig. 5. The length of the deflecting electrodes 33 and 34 to which an alternating voltage is applied from a-source measured in a direction parallel to the beam, is approximately The length of the auxiliary deflecting electrodes 35, 36 and 3? is consequently A. The required charge for a given deflection in the arrangement of Figs. 5, 6 and 7 is /2, A; and A; respectively of that which would be required, if the deflecting electrodes to which the alternating voltages are supplied were directly opposite one another.

Fig. 8 shows a further embodiment, in which the length of the deflecting electrode 38 plus the length of the auxiliary deflecting electrode 39 is approximately V. This system is, in effect, a combination of two systems, in which the transit time of the electrons is not a factor of importance. The length of the entire system is, how ever, such that the transit time would tend to be influential if the whole system were traversed and would therefore give rise to three pairs of auxiliary deflecting electrodes, i. e. 39, 40, 5|, 62 and 43a, 531). The latter electrodes which are on one side of the electrode beam are directly interconnected, as far as alternating voltages are concerned, by way of a condenser 43. The operation of the system shown in Fig. 8 may be explained as follows:

A signal voltage is applied between electrodes 38 and 44 from a source 50. If at a given instant electrode 38 is positive, and the other defleeting electrode 44 negative, the following charges are induced in the auxiliary deflecting electrodes: In electrode 50 a negative charge; in electrode 39 a positive charge; in 43a, consequently, a negative charge; in @311 a positive charge; in 4| a negative charge and in 42, con sequently, a positive charge. An electron which is subjected to deflection in systems 33, 40 and 38, am will be subjected to an identical deflection";

in the same direction in systems 4|, cab and 42, 44 since during the passage through the deflection system the voltage of electrode 44 and hence that of 42, 41 and 43b change their polarities.

The charge required to be supplied through the connecting wires of the deflecting electrodes 38 and M is approximately one fourth of that which would be required to be supplied to ensure equal deflection sensitivity, if the electrodes 33 and M were opposite each other.

The foregoing figures show electrode systems in which the auxiliary deflecting electrodes and the deflecting electrode are approximately parallel to one another. This is not always essential and one embodiment of the invention in which this is not the case is shown in Fig. 9, in which 45 and it designate the deflecting electrodes to which an alternating voltage is applied from a source 56 and Al, A8 the auxiliary deflecting electrodes. It may be seen from this figure that the electrodes 4'! and 58 are directly interconnected. If the period of the voltage which is fed to the deflecting electrodes 45 and 46 is high compared with the time in which the electrons pass through the system, each electron subjected to deflection in a given direction between the electrodes 35 and 4'! will be subjected between the electrodes 46 and 48 to a deflection which is at right angles to the first deflection and is in phase therewith. This will result in a deflection '6 of the electron beam at an angle of 45 with the direction of the deflection produced by the electrodes 45 and 4! alone. If the electrodes 46 and '48 are not at right angles to the planes ofthe electrodes is and 41, a deflection at a diflerent angle may be obtained.

If the period of the voltage fed to the electrodes 45 and 4i becomes of the same order of magnitude as the transit time of the electrons in the deflection system, this system is capable of producing elliptical Lissajou figures. If, in the system shown, the electrons traverse the distance between the centre of the line connecting the centres of the electrodes s5 and ll and the centre of the line connecting the centres of the electrodes '36 and 48 in one quarter of the period of the oscillation fed to the electrodes 45, 46, the electron beam performs a circular movement.

What I claim is:

1. An electric discharge tube comprising an electron beam source, an electron beam receiving element spaced from said source in the path of the electron beam, and an electrostatic beam deflection electrode system interposed between the source and the beam receiving element for defleeting the beam in accordance with an electric signal from a source of signal potential, said electrode system comprising a plurality of capacitative elements of equal capacitance each of which comprises a pair of spaced electrodes on opposite sides of the path of the electron beam, and means connecting all of said elements in series relationship with said source of signal potential whereby a reduced signal current is required for a given deflection.

2. An electric discharge tube comprising an electron beam source, an electron beam receiving element spaced from said source in the path of the electron beam, and an electrostatic beam deflection electrode system interposed between the source and the beam receiving element for deflecting the beam in accordance With an electric signal from a source of signal potential, said electrode system comprising first, second, third and fourth capacitative elements of equal capacitance, each of said elements comprising a pair of electrodes disposed on opposite sides of the electron beam, means connecting one of said electrodes of said first element to one of said electrodes of said third element on the opposite side of the electron beam, means connecting the other of said electrodes of said third element to one of said electrodes of said second element on the opposite side of said electron beam, means connecting the other of said electrodes of said second element to one of said electrodes of said fourth element on the opposite side of said path, and means connecting the other of said electrodes of said first and fourth elements in series relationship with said source of signal potential whereby a reduced signal current is required for a given deflection.

3. An electric discharge tube comprising an electron beam source, an electron beam receiving element spaced from said sourc in the path of the electron beam, and an electrostatic beam deflection electrode system interposed between the source and the beam receiving element for deflecting the beam in accordance with an electric signal from a source of signal potential, said electrode system comprising a plurality of capacitative elements of equal capacity each of which comprises a pair of spaced electrodes on opposite sides of the path of the electron beam, at least one of said electrodes on one side of the path of the beam being integral with an adjacent electrode on said one side of the path, and means connecting all of said elements in series relationship with said source of signal potential whereby a reduced signal current is required for a given deflection.

4. An electric discharge tube comprising an electron beam source, an electron beam receiving element spaced from said source in the path of the electron beam, and an electrostatic beam deflection electrode system interposed between the source and the beam receiving element for deflecting the beam in accordance with an electric signal from a source of signal potential, said electrode system comprising a plurality of capacitative elements including a pair of end elements and at least one intermediate element all of equal capacitance, said capacitative elements comprising a pair of outer electrodes and a plurality of auxiliary electrodes, each of said end elements being constituted by an outer electrode and an end portion of an auxiliary electrode on opposite sides of the path of the electron beam and each of said intermediate elements being constituted by opposing end portions of said auxiliary electrodes, and means connecting said outer electrodes in series relationship with said source of signal potential whereby a reduced signal current is required for a given deflection.

5. An electric discharge tube comprising an electron beam source, an electron beam receiving element spaced from said source in the path of the electron beam, and an electrostatic beam deflection electrode system interposed between the source and the beam receiving element for deflecting the beam in accordance with an electric signal from a source of signal potential, said electrode system comprising first, second, third and fourth capacitative elements of equal capacity each of which comprises a pair of electrodes disposed on opposite sides of the electron beam, means connecting one of said electrodes of said first element on a given side of said path to one of said electrodes of said second element on the other side of said path, means connecting one of said electrodes of said fourth element on said given side to one of said electrodes of said third element on the other side of said path, means capacitatively coupling the other of said electrodes of said second and third elements, and means connecting the other of said electrodes of said first and fourth capacitative elements in series relationship with said source of signal potential whereby a reduced signal current is required for a given deflection.

6. An electric discharge tube comprising an electron beam source, an electron beam receiving element spaced from said source in the path of the electron beam and an electrostatic beam deflection electrode system interposed between the source and the beam receiving element for deflecting the beam in accordance with an electric signal from a source of signal potential, said electrode system comprising a pair of capacitative elements of equal capacitance disposed at right angles to one another, each of which comprises a pair of spaced electrodes on opposite sides of the path of the electron beam, and means connecting said elements in series relationship with said source of signal potential whereby a reduced signal current is required for a given deflection.

ADRIAN'US J OHANNES WILHELMUS MARIE VAN OVERBEEK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,932,084 Opsahl Oct. 24, 1933 2,103,507 Zworykin Dec. 28, 1937 2,118,867 Schlesinger May 31, 1938 2,147,825 Zworykin et al Feb. 21, 1939 2,175,697 Nelson Oct. 10, 1939 2,182,382 Hollmann Dec. 5, 1939 2,193,539 Shel-by Mar. 12, 1940 2,221,115 Shepard Nov. 12, 1940 2,228,958 Hinsch Jan. 14, 1941 2,232,158 Banks Feb, 18, 1941 2,240,304 Koch Apr. 29, 1941 2,293,539 Gray Aug. 18, 1942 2,326,877 Mueller Aug. 17, 1943 2,459,724 Selgin Jan. 18, 1949 

